fix(config): fix `loadConfig()` failing with "missing loader for extension"

[tido64]

Summary:

Part 2 of https://github.com/react-native-community/cli/pull/2549 because I had missed a spot, even though I thought I had tested this properly.

Test Plan:

This is enough to trigger the error:

node -p 'require("@react-native-community/cli").loadConfig({})'

Checklist

• [x] Documentation is up to date to reflect these changes.
• [x] Follows commit message convention described in CONTRIBUTING.md

[thymikee]

Released in v15.1.2

[tido64]

Released in v15.1.2

Thanks for the super quick turnaround!